Given that we know what the end of the timeline looks like from the very beginning of the book it made it rather simple to keep in mind where each story arc was in relation to the others.

The main problems with the timeline are that there are several instances where BSand seemed to skip ahead. Things like Mat early in the book being much closer to Egwene/Rand timeline than he should have been, and Perrin still being at the end of TGS in one chapter then seemingly only days later has caught up to the rest of the story lines by the end of TOM. But even those issues are easy enough to shrug off.

My bigger problems are with BSands lack of feel for many characters. He still doesn't get Mat, Graendal and Moridin were a mess and Faile may as well be a different character! I think he missed a little with Elayne too, not as noticeable as some of the others, but personally I found her a character a little flat in this book.

I also thought the pacing of the book was a bigger problem than the timeline. It felt very rushed to me. Perrin needing to master the wolf dream in a matter of weeks felt contrived rather than suspenseful, Elayne and Mat having one quick meeting before she essentially agreed to build the Dragons, even Moiraine's rescue felt rushed.

I'm not sure I agree with how DomA would have cut the books as that could have made TGS and TOM very hard to follow and quite possibly too slow moving overall ... I think we would all have been very disappointed in TGS if it had ended for all story lines at the same point, but with little in the way of resolutions. No one wanted another volume of AS Tower division or Rand still going insane so IMO best to wrap them up and get those plot lines moving forward again.

Egwene and Rand clearly had the most left to accomplish at the start of TGS and would have needed more attention than the others anyway you look at it, Elayne had already claimed her throne, Perrin had destroyed the Shaido and Masema, and Mat was already pointed toward Genji and Elayne to build the Dragons ... there wasn't much story to tell around any of them by the start of TGS, not until Rand and Egwene had wrapped up a few things on their ends. I'd be willing to bet that they chose to split the books on story line because many of the things Elayne/Perrin/Mat were up to needed to happen after Rand's epiphany and Egwene's unification of the Tower.

If you get right down to it Elayne essentially did nothing in this book except grab Cairhien and build Dragons, Perrin was on his own self realization journey but didn't really accomplish a lot in the book. Mat killed the Gholam and rescued Moiraine. None of these plot lines was necessary to TGS and could have happened at any point in the timeline. Did it make TOM weaker? Probably, but IMO it also made TGS a stronger book.